4ntm
From Proteopedia
QueD soaked with sepiapterin (selenomethionine substituted protein)
Structural highlights
FunctionQUED_ECOLI Catalyzes the conversion of 7,8-dihydroneopterin triphosphate (H2NTP) to 6-carboxy-5,6,7,8-tetrahydropterin (CPH4) and acetaldehyde. Can also convert 6-pyruvoyltetrahydropterin (PPH4) and sepiapterin to CPH4; these 2 compounds are probably intermediates in the reaction from H2NTP. Publication Abstract from PubMed6-Pyruvoyltetrahydropterin synthase (PTPS) homologs in both mammals and bacteria catalyze distinct reactions using the same 7,8-dihydroneopterin triphosphate substrate. The mammalian enzyme converts 7,8-dihydroneopterin triphosphate to 6-pyruvoyltetrahydropterin, whereas the bacterial enzyme catalyzes the formation of 6-carboxy-5,6,7,8-tetrahydropterin. To understand the basis for the differential activities we determined the crystal structure of a bacterial PTPS homolog in the presence and absence of various ligands. Comparison to mammalian structures revealed that although the active sites are nearly structurally identical, the bacterial enzyme houses a His/Asp dyad that is absent from the mammalian protein. Steady state and time-resolved kinetic analysis of the reaction catalyzed by the bacterial homolog revealed that these residues are responsible for the catalytic divergence. This study demonstrates how small variations in the active site can lead to the emergence of new functions in existing protein folds. Biochemical and Structural Studies of 6-Carboxy-5,6,7,8-tetrahydropterin Synthase Reveal the Molecular Basis of Catalytic Promiscuity within the Tunnel-fold Superfamily.,Miles ZD, Roberts SA, McCarty RM, Bandarian V J Biol Chem. 2014 Aug 22;289(34):23641-52. doi: 10.1074/jbc.M114.555680. Epub, 2014 Jul 2. PMID:24990950[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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